1. Field of the Invention
The present invention relates to an on-demand type ink-jet printing apparatus, and an ink-jet printing head which can be equipped in the ink-jet printing apparatus.
2. Description of the Related Art
In general, an ink-jet printing apparatus can be generally classified into a continuous ejection type (hereinafter also referred to as continuous type) and an on-demand type. The former continuous type ink-jet printing apparatus continuously ejects ink droplets from a fine nozzle at a predetermined period, and deposits the ink droplets at predetermined positions on printing paper as a printing medium, by subsequently applying an electric charge on the ink droplets for causing deflection toward the predetermined positions. Advantages of such continuous type ink-jet printing apparatus are high frequency response, capability of making the ink-droplet more fine, capability of high speed printing despite of single nozzle, and capability of performing printing of an image with high resolution. On the other hand, since such continuous type ink-jet printing apparatus requires a mechanism for collecting inks, overall construction becomes bulky and thus is not well suited for multiple nozzle construction.
In contrast to this, in the case of the former on-demand type ink-jet printing apparatus, ink can be deposited at predetermined positions on the printing paper as a printing medium by controlling ink ejection from nozzles corresponding to the position to perform image printing in a system ejecting an ink using a pressure by deformation of a piezoelectric element provided in a plurality of fine nozzles or a pressure generated by volume expansion of a bubble generated by heating of the ink for causing film boiling by a heating element. The ink-jet printing apparatus of this type is advantageous in easiness for adaptation to multiple nozzle construction for simple construction and in realization of compact and inexpensive image printing apparatus. On the other hand, since the ink does not always flow through the nozzle, plugging of the nozzle due to drying of the ink, variation of quality of the ink, penetration of dust and so on can be caused. Therefore, a recovery mechanism for solving the problem of plugging becomes inherent.
On the other hand, in the foregoing two types of ink-jet printing apparatus, a common problem is encountered in difficulty of density modulation of the ink droplet. Therefore, expression of more precise gradation in an intermediate tone can be realized only by a system controlling size of the ink droplets among a plurality of steps of sizes of the ink droplets, and by a system performing ejection from different nozzles with a plurality of mutually different densities of inks.
The highest quality of more precise gradation expression is achieved by a system performing printing with varying density of the ink droplets without varying size of the ink droplet.
Such system in the continuous type ink-jet printing apparatus has been proposed in U.S. Pat. No. 4,614,953. On the other hand, such system in the on-demand type ink-jet printing apparatus has been proposed in Japanese Patent Application Laid-open No. 5-201024 (1993) (U.S. Pat. No. 5,371,529).
However, in U.S. Pat. No. 4,614,953 directed to the continuous type ink-jet printing apparatus, difficulty in employing a plurality of nozzles as drawback of the continuous type is not mentioned. Therefore, the continuous type is not applicable for compact and inexpensive printing apparatus.
On the other hand, in Japanese Patent Application Laid-open No. 5-201024 (1993) (U.S. Pat. No. 5,371,529) directed to the on-demand type ink-jet printing apparatus, a mechanism for mixing the inks per the ejection nozzle is disclosed. However, due to the presence of such mixing mechanism, down-sizing can be hindered upon employing the multiple nozzle construction. Furthermore, fluctuation of the ink density between the nozzles can be caused easily.
The present invention has been worked out for solving the problems set forth above. It is a first object of the present invention to provide an ink-jet printing head and an ink-jet printing apparatus which can reduce fluctuation of density of an ink ejected from each nozzle by ejecting ink of different densities from the same nozzle without varying size of an ink droplet, or by controlling ejection of a mixture ink, in which a plurality of inks are mixed, for forming an image.
A second object of the present invention is to provide an ink-jet printing head and an ink-jet printing apparatus which can minimize consumption of ink.
A third object of the present invention is to provide various modes of implementation associated with the ink-jet printing head and the ink-jet printing apparatus according to the present invention.
To achieve the first object of the present invention, there is provided an ink-jet printing head comprising:
a plurality of ejection openings for ejecting ink;
a plurality of ink passages respectively communicated with the plurality of ejection openings;
means provided in the plurality of ink passages for ejecting ink;
a mixing liquid chamber connected to the plurality of ink passages in common;
a plurality of individual liquid chambers supplying ink to the mixing liquid chamber; and
a valve mechanism, provided between each the individual liquid chamber and the mixing liquid chamber, for controlling a supply amount of the ink supplied from the individual liquid chamber.
With the printing head constructed as set forth above, by providing one mixing liquid chamber communicated with a plurality of ejection openings and a plurality of ink supply passages and by providing control means for controlling ink supply amount to the mixing liquid chamber, it becomes possible to vary the density with maintaining the size of the ink droplet constant to realize printing with higher printing quality. On the other hand, by adjusting the ink density in the mixing liquid chamber, the ink with different densities can be ejected without using a plurality of printing heads and preliminarily prepared inks with different densities. For example, a colored ink is filled in one of two individual liquid chambers communicated with the mixing liquid chamber, and an achromatic ink is filled in the other individual chamber to obtain an ink of the density of half of the colored ink by mixing the colored ink and the achromatic ink within the mixing liquid chamber in a proportion of 1:1. Furthermore, it is possible to fill the ink of cyan color in one of the individual liquid chambers and to fill the ink of yellow color in the other individual liquid chamber to obtain the ink of green color by mixing both inks in a proportion of 1:1 within the mixing liquid chamber.
Here, the ink-jet printing head as claimed in claim 1, which further may comprise ink moving means for moving the ink by applying energy to the ink sufficient for moving the ink from the individual liquid chamber to the mixing liquid chamber.
The plurality of individual liquid chambers may contain inks having mutually different compositions respectively.
A washing liquid which is supplied for discharging liquid in the mixing liquid chamber, may be stored in one of the plurality of individual liquid chambers.
A plurality of the valve mechanisms may be provided for each of the individual liquid chambers.
The plurality of valve mechanisms may be provided corresponding to ink passages having different open areas between the individual liquid chamber and the mixing liquid chamber.
The plurality of valve mechanisms may be provided corresponding to ink passages having the same open area between the individual liquid chamber and the mixing liquid chamber.
A partitioning wall serving as ink mixing means may be provided in the mixing liquid chamber for promoting mixing of the inks.
A discharge passage for discharging a mixture ink in the mixing liquid chamber.
A plurality of ejection openings may be arranged in a row and the discharge passage may be communicated with a discharge opening arranged on an extension in a row direction of the ejection openings.
The discharge passage may be arranged in a direction intersecting with a supply direction of the ink from the individual liquid chamber to the mixing liquid chamber.
To achieve the second object of the present invention, there is provided an ink-jet printing head comprising:
a plurality of ejection openings for ejecting ink;
a plurality of ink passages respectively communicated with the plurality of ejection openings;
ink ejection means provided in the plurality of ink passages for ejecting ink;
an ejection liquid chamber connected to the plurality of ink passages in common;
at least one mixing liquid chamber connected to the ejection liquid chamber;
a plurality of individual liquid chambers supplying ink to the mixing liquid chamber; and
first path control means, provided between the individual liquid chambers and the mixing liquid chamber, for controlling a supply amount of the inks supplied from the individual liquid chambers.
With the construction set forth above, by providing the intermediate liquid chamber for storing the mixture ink between the mixing liquid chamber and the ejection liquid chamber, an ink consuming amount upon switching of inks can be restricted to only an ink amount in the ejection liquid chamber to lower the ink consuming amount associating with switching of the ink and to shorten the switching period. On the other hand, by providing a plurality of intermediate liquid chambers to establish a plurality of passages from the mixing liquid chamber to the ejection liquid chamber to perform switching of the ink with selecting the passage. After switching, with performing mixing operation again, the ink having the same mixture ratio can be ejected.
Here, the ink-jet printing head as claimed in claim 12, which further may comprise an intermediate liquid chamber arranged between the mixing liquid chamber and the ejection liquid chamber.
A plurality of the intermediate liquid chambers may provided.
On the other hand, the present invention provides various associated aspects having particular effect in addition to the first object or independently.
According to another aspect of the present invention, here is provided an ink-jet printing head comprising:
a plurality of ejection openings arranged in a row and for ejecting ink;
a plurality of ink passages communicated with the plurality of ejection openings respectively;
ink ejecting means provided in the plurality of ink passages for ejecting ink;
a common liquid chamber connected to the plurality of ink passages in common;
an ink supply portion for supplying ink to the common liquid chamber;
control means, provided between the ink supply portion and the common liquid chamber, for controlling a supply amount of ink supplied from the ink supply portion; and
an atmosphere communication opening, arranged on an extension of the row of the ink ejection openings, for communicating the common liquid chamber with atmosphere.
With the construction set forth above, by using the atmosphere communication opening as an atmospheric air suction opening into the head, cleaning of the common liquid chamber and cleaning operation of the printing nozzle can be facilitated and assured. Also, by using the atmosphere communication opening as an ink suction opening, quicker ink suction operation than that in the case where ink suction is performed only through the normal printing nozzles, can be realized. Furthermore, by using one atmosphere communication opening for two ways as an atmosphere suction opening and an ink discharge opening, the foregoing superior effect can be achieved with simple construction of the printing head.
According to yet another aspect of the present invention, there is provided a liquid-jet printing head comprising:
a plurality of ejection openings for ejecting liquid;
a plurality of liquid passages communicated with the plurality of ejection openings;
a first liquid chamber connected to the plurality of liquid passages in common;
a liquid supply portion supplying the liquid to the first liquid chamber; and
a second liquid chamber storing a washing liquid to be supplied for discharging the liquid in the first liquid chamber.
With the construction set forth above, a liquid ejecting apparatus and a liquid ejection head which are compact and inexpensive and can reproduce more precise gradation by exchanging only ink tanks without exchanging the printing head. Also, it becomes possible to provide the liquid ejecting apparatus and the liquid ejection head which can quickly and certainly switch the ink in the liquid chamber in the printing head without causing admixing of the colors in simple construction.
To achieve also the first object of the present invention, there is provided an ink-jet printing apparatus performing printing on a printing medium by ejecting ink thereon, comprising:
an ink-jet printing head having an ink chamber storing the ink to be ejected and a plurality of ink supply passages capable of supplying mutually different kinds of inks to the ink chamber;
ink supply means capable of supplying a plurality of kinds of inks which have the same composition and different density, to the plurality of ink supply passages respectively; and
selecting means for selecting kind of the ink to be supplied into the ink chamber from the plurality of ink supply passages on the basis of an image data.
Here, the selecting means may select one of the plurality of ink supply passages for supplying the ink having a density corresponding to a density level of the image data into the ink chamber from the selected ink supply passage.
According to yet another aspect of the present invention, there is provided an ink-jet printing apparatus performing printing on a printing medium by ejecting ink thereon, comprising:
an ink-jet printing head having an ink chamber storing the ink to be ejected and a plurality of ink supply passages capable of supplying mutually different kinds of inks to the ink chamber;
ink supply means for supplying a first ink having a predetermined density to at least one of the plurality of ink supply passages and a second ink reducing density of the first ink without varying composition thereof, to at least another one of the plurality of ink supply passages; and
selecting means for selecting kind of the ink to be supplied into the ink chamber from the plurality of ink supply passages on the basis of an image data.
With the construction set forth above, it becomes possible to provide an ink-jet printing apparatus and an ink-jet printing method to realize recording, such as printing, with more precise gradation using the ink-jet printing head which can eject inks of different ink density from the same nozzle without varying the size of the ink droplet with maintaining advantages of the on-demand type ink-jet printing system.
Here, the selection means may select more than or equal to two of the plurality of ink supply passages for mixing the first ink and the second ink from the selected ink supply passages in the ink chamber for preparing an ink of a density corresponding to a density level of the image data.
The ink-jet printing apparatus as claimed in claim 19, which further may comprise a control means for making overlapping print an image on the printing medium for more than or equal to two times when the selection means supplies an ink having density lower than the density level of the image data to the ink chamber.
The selection means may vary kind of the ink to be supplied to the ink chamber for more than or equal top one time when the image is printed in overlapping manner for more than or equal to two times by the control means.
To achieve also the second object of the present invention, there is provided an ink- jet printing apparatus for performing printing on a printing medium by ejecting ink, comprising:
a printing portion having ejection opening s for ejecting the ink and an ink mixing chamber for mixing the ink to be ejected;
a target density setting portion for setting an ink density having relatively high use frequency as a target ink density on the basis of an image data representative of an image to be printed by the printing portion;
a mixture ratio calculating portion for calculating a mixture ratio of a residual ink in the ink mixing chamber of the printing portion and an ink of predetermined density supplied to the ink mixing chamber so that the ink density of the ink mixing chamber of the printing portion becomes the target ink density on the basis of the target ink density data set by the target density setting portion;
an ink density adjustment control portion for adjusting and controlling the ink density in the ink mixing chamber prepared by mixing the residual ink in the ink mixing chamber of the printing portion and the ink from an ink supply portion supplying a predetermined amount of the ink having predetermined density to the ink mixing chamber, for establishing the target ink density on the basis of the data representative of the mixture ratio from the mixture ratio calculating portion; and
a printing operation control portion for making the printing portion to perform printing operation on the basis of the image data.
Here, the ink density adjustment control portion may comprise:
a discharge operation control portion for making an ink discharge means to perform discharge operation for discharging a predetermined amount of the residual ink in the ink mixing chamber on the basis of data representative of the mixture ratio from the mixture ratio calculating portion; and
a supply operation control portion for making an ink supply means to perform ink supply operation for supplying a predetermined amount of the ink with the predetermined density to the ink mixing chamber on the basis of the data representative of the mixture ratio from the mixture ratio calculating portion.
The ink supply means may comprise:
a plurality of ink chambers respectively storing inks having mutually different ink densities;
control valves, provided in liquid passages for introducing the inks from the plurality of ink chambers to the ink mixing chamber, for selectively adjusting an ink supply amount introduced into the ink mixing chamber; and
energy generating element s arranged adjacent the control valves and causing the ink to flow from the ink chambers through the control valve s.
The target density setting portion may vary the target ink density on the basis of the image data per one scan of the printing portion for a printing surface of the printing medium.
The printing operation control portion for making the printing portion to perform printing operation on the basis of the image data may make to perform printing operation from a portion to be printed with relatively high ink density to a portion to be printed with relatively low ink density in the image to be formed on the printing surface of the printing medium.
The supply operation control means, which may make the ink supply means to perform ink supply operation on the basis of the data representative of the mixture ratio from the mixture ratio calculating portion, may make the ink supply means to perform ink supply operation such that a supply amount is proportional to an ink ejection amount of the printing portion during printing operation of the printing portion.
According to yet another aspect of the present invention, there is provided an ink-jet printing apparatus comprising;
an ink-jet printing head including:
a plurality of ejection openings arranged in a row and ejecting ink;
a plurality of ink passages respectively communicated with the plurality of ejection openings;
an ink ejection means provided in the plurality of ink passages;
a common liquid chamber connected to the plurality of ink passages in common;
an ink supply portion for supplying the ink to the common liquid chamber;
control means, provided between the ink supply portion and the common liquid chamber, for controlling an supply amount of the ink supplied from the ink supply portion;
an atmosphere communication opening, arranged on an extension of the row of the ink ejection openings, for communicating the common liquid chamber with outside;
first capping means for placing the ink eject ion openings of the printing head within an sealingly enclosed space;
first suction means for reducing a pressure within the enclosed space between the first capping means and the printing head;
second capping means for placing the atmosphere communication opening of the printing head within a sealingly enclosed space;
second suction means for reducing a pressure within the enclosed space between the second capping means and the printing head; and
wherein the first suction means and the second suction means are driven at respectively independent timing.
Here, the ink-jet printing apparatus as claimed in claim 29, which may further comprise a carriage for moving the printing head for scanning, and a waste ink absorbing body extending along a scanning direction of the printing head at a position overlapping with a range in which printing by the printing head on the printing medium can be performed, for receiving a waste ink discharged from the printing head.
The printing head may discharge the waste ink toward the waste ink absorbing body during movement.